1. Field of the Invention
The present invention relates to a length measuring or map meter apparatus for measuring the length of an object or length between two points, or a distance measure for measuring the distance between two points on a map.
2. Description of the Related Art
An apparatus is known which rotates a rotational disc along a line connecting two points and detects the amount of rotation of the disc to thereby measure the distance or length between the two points. Such a measuring apparatus is disclosed in, for example, Japanese Patent Disclsoure Nos. 61-169710 and 61-149801.
U.S Pat. No. 3,999,198 discloses such a measuring apparatus assembled in a wrist watch.
A technique concerning a measuring apparatus assembled in a wrist watch has been also described in U.S. patent application Ser. No. 315,526 filed on Feb. 24, 1989 U.S. Pat. No. 4,914,831 (Assignee: Casio Computer Co., Ltd. of the present invention). This type of a length measuring apparatus is used as, for example, a map meter. This map meter is used for measuring point to point distances on a map and indicating real distances upon correction by multiplying the above point to point distances by the scale reduction data to the map, which have been input to the map meter.
In this type of map meter, in order to obtain a plurality of distance data between a series of points, it is necessary to clear a distance data previously obtained every time other distance data is to be measured, and therefore it is also necessary to make notes of distance data between points. Further, in conventional map meters, scale reduction data must be set by means of the input keys in accordance with the scale reduction to the map to be used, every time measurement is executed. Accordingly, disregarding that in general, scale reductions to maps are limited to several scales, these map meters must be reset every measurement by inputting scale reduction data, which requires troublesome operations.